Let's assume that Bitcoin has become the universal currency for the sake of simplicity
You did not elaborate, of exactly how infinite divisibility makes the "rich even richer" and the "poor poorer" in "the long run". I doubt that your argument is really valid, because in contrast to owning fiat money with virtually unlimited supply, owning Bitcoin is not subject to inflationary devaluation. The opposite is true: With increasing Bitcoin use, the purchasing power of the same amount of Bitcoin owned will likely increase since the total number of Bitcoin is fixed. Divisibility is a necessity to make payments feasible in the context of increasing buying power - it does in no way reduce the value of one's holdings
Indeed, you are entitled to think that my point is not valid. Some morons even discard the whole idea of infinite divisibility as being nonsensical and meaningless altogether without ever realizing that this is no more than a catchy metaphor, a convenient figure of speech, lol. But let's return to our muttons now. Do you agree that unlimited fiat supply makes the rich richer and the poor poorer, and clearly understand how that happens?
Without understanding this you won't be able to fully grasp why my point is in fact valid in respect to Bitcoin as well